Principles of Probabilistic Regional Mineral Resource Estimation

Five principal sources of uncertainty in quantitative mineral resource estimation are listed and illustrated by means of a simple example (mosaic model) and a case history study for large copper deposits in the Abitibi area of the Canadian Shield. Abitibi copper potential originally was estimated on the basis of 1968 estimates of production and reserves totalling 3.12 Mt Cu. This prognostication now could be evaluated on the basis of 2008 copper production and reserves totalling 9.50 Mt Cu. An earlier hindsight study performed on the basis of 1977 data (totalling 5.23 Mt Cu) showed seven new discoveries occurring either in the immediate vicinities of known deposits or on broad regional copper anomalies predicted from the 1968 inputs. By 1977, the global geographic distribution pattern of large copper deposits in the Abitibi area had stabilized. During the next 30 years, new copper was essentially found close to existing deposits, much of it deeper down in the Earth's crust. In this paper, uncertainties associated with copper ore tonnage are analyzed by comparison of 2008 data with 1968 data using (a) log-log plots of size versus rank, and (b) lognormal QQ-plots. Straight lines fitted by least squares on these plots show that 1968 slopes provide good estimates of 2008 slopes but 1968 intercepts are much less than 2008 intercepts. In each linear log-weight versus log-rank plot, the slope is related to fractal dimension of a Pareto frequency distribution, and in a lognormal QQ-plot it is determined by logarithmic variance. The difference between 2008 and 1968 intercepts represents the increase in copper ore production and reserves from 1968 to 2008. The Pareto model fits actual copper and massive sulphides increase over the past 40 years better than the lognormal frequency distribution model for 10 km×10 km cells on favorable environments in the Abitibi area.      

Geology and mineralization of the Tiegelongnan supergiant porphyry-epithermal Cu (Au,Ag) deposit (10 Mt) in western Tibet,China: A review

The Tiegelongnan Cu(Au,Ag)deposit in central Tibet contains more than 10 Mt of copper ranking 29 th in the world.It is characterized by typical porphyry-epithermal alteration and mineralization.In order to improve the understanding of porphyry-epithermal copper deposit in Tibet,new zircon U-Pb age and sulfur isotope data along with published data in the Tiegelongnan are presented to investigate the formation and preservation mechanism.Ore-related intrusive rocks in the Tiegelongnan including Early Cretaceous(about 120 Ma)granodiorite porphyry and diorite porphyry are closely related to the northward subduction of Bangongco-Nujiang ocean.Sulfur mainly comes from deep magma,and ore-forming fluid is affected by both magmatic and meteoric water.The metallogenic setting of Tiegelongnan is consistent with those of Andean porphyry copper deposits in South America.The cover of the Meiriqiecuo Formation volcanic rocks,Lhasa-Qiangtang collision and India-Eurasian collision have significance in the preservation and uplift of the deposit.The formation,preservation and discovery of Tiegelongnan play an important role in exploration of ancient porphyry-epithermal deposits in Tibet.     

Carbon cycle variability in tropical Atlantic across two Early Eocene hyperthermals

Early Eocene hyperthermals are geologically short-lived global warming events and represent fundamental perturbations to the global carbon cycle and the Earth’s ecosystem due to massive additions of isotopically light carbon to the ocean-atmosphere system.They serve as ancient analogs for understanding how the oceanic carbonate system and surface-ocean ecosystem would respond to ongoing and future climate change.Here,we present a continuous carbonate record across the Eocene Thermal Maximum 2(ETM2 or H1,ca.54.1 Ma)and H2(ca.54 Ma)events from an expanded section at Ocean Drilling Program Site 1258 in tropical Atlantic.The abundant calcareous nannofossils and moderate carbonate content throughout the studied interval suggest this record was deposited above the calcite compensation depth(CCD),but below the lysocline and under the influence of terrestrial dilution.An Earth system model cGENIE is used to simulate the carbon cycle dynamics across the ETM2 and H2 to offer insights on the mechanism of the rapid warming and subsequent recovery in climate and ecosystem.The model suggests moderate changes in ocean pH(0.1–0.2 unit)for the two scenarios,biogenic methane from a rechargeable methane capacitor and organic matter oxidation from thawing of the permafrost.These pH changes are consistent with a recent independent pH estimate across the ETM2 using boron isotopes.The carbon emission flux during the ETM2 is at least an order of magnitude smaller than that during the Paleocene–Eocene Thermal Maximum(PETM)(0.015–0.05 Pg C yr^-1vs.0.3–1.7 Pg C yr^-1).The comparable pre-and post-event carbonate contents suggest the lysocline did not over deepen following the ETM2 at this tropical Atlantic site,indicating spatial heterogeneity in the carbonate system due to strong dilution influence from terrestrial weathering and riverine discharge at Site 1258.     

Geochronological and geochemical constraints on the petrogenesis of late Mesoproterozoic mafic and granitic rocks in the southwestern Yangtze Block

Late Mesoproterozoic igneous rocks in the SW Yangtze Block are important for understanding the role of it in reconstruction of the Rodinia supercontinent.In the present study,we report new geochronological,geochemical,and Nd-Hf isotopic data for the Cuoke plagioclase amphibolites and granites in the SW Yangtze Block.Geochronological results show that the plagioclase amphibolites and granites have similar late Mesoproterozoic zircon U-Pb ages of 1168-1162 Ma,constituting a bimodal igneous assemblage.The plagioclase amphibolites have high and variable TiO2 contents(1.15-4.30 wt.%)and Mg#(34-66)values,similar to the tholeiitic series.They are characterized by enrichment in LREEs and LILEs,and have OIB-like affinities with positive Nb and Ta anomalies.The plagioclase amphibolites have positive whole-rockεNd(t)(+3.2 to+4.3)and zirconεHf(t)(+4.3 to+10.7)values,indicating that they were derived from an OIB-like asthenospheric mantle source.The granites belong to the reduced peralkaline A-type series and have negativeεNd(t)value of-6.0 andεHf(t)values of-5.8 to-13.8,indicating a derivation from the partial melting of ancient mafic lower crust.In combination with the~1.05-1.02 Ga bimodal igneous assemblage in the SW Yangtze Block,we propose that the Cuoke 1168-1162 Ma igneous rocks were likely formed in a continental rift basin and argue against the existance of Grenvillian Orogen in the SW Yangtze Block during the late Mesoproterozoic.     

Analysis of prospecting polymetallic metallogenic belts by comprehensive geophysical method

This paper is based on the analysis and research on the silver-lead-zinc polymetallic ore in New Ballyhoo Banner in southern Manzhouli of Inner Mongolia.Because metal mineralization brings rock formations,the geophysical features such as low resistivity,high polarization rate and uneven distribution of magnetization,the comprehensive geophysical methods are adopted including high-precision magnetic measurement,high-power induced polarization,IP field middle gradient and controlled source audio-frequency magnetotellurics.In the survey work of multi-metal ore deposits,from surface sweeping to single point measurement,and from single point to section going deeper layer by layer,the resolution of measurement is continuously improved,and various geophysical methods support and complement each other,so explorers can successfully predict the direction,scale and volume of the metallogenic belts in conjunction with geochemical exploration,geological survey and drilling.It has provided a strong basis for completing the exploration task of predicting the reserve volume of ore bodies.The research conclusions of this exploration case have thus a high reference value in the same type of exploration work.     

利用Grapher绘制彩色渐变剖面平面图

在物探扫面工作中,有大量的剖面数据需要绘制成剖面平面图,要求寻找一个高效快速的制图方法.通过对Grapher 自动化功能的分析和实践,编制程序实现了快速绘制彩色渐变剖面平面图的需求,说明利用自动化脚本能够在获得精美图件的同时,可以极大地提高作图效率.     

冷生风化作用对边坡稳定性影响

The experiment shows that considerable influence on density rock properties are subjected by nival weathering conditions. The main parameter defining the rock suitability for solution various engineering and geological problems is its firmness limit on single axis pressing. The firmness properties of sandstone being in absolutely dry condition for Kabakta suite at the beginning of investigation was 64.7 MPa, for Nerungri suite sandstones it was 48. 7 MPa. The investigations showed how much the nival conditions of cryohypergenesis of rock sandstones in Kabakta and Nerungri suites have destructive influence in comparison with aquale and more over aerale conditions. In the aerale conditions sedimentary rock firmness of Kabakta suite decreased to 23.2 MPa, in aquale conditions to 16.5, and in the nivale conditions to 8.9 MPa. In Nerungri suite sandstones are according to 17.7 MPa, 11.1 MPa, and 6 MPa after 300 freezing and thawing cycles. The common sandstone firmness decrease of Kabakta suite was 25 %,of Nerungri suite it was 23.8%. Marlstone samples after 400 FTC decrease to 62% in the nivale conditions and to 33 % in the aerale conditions. After 3～5 years of exploitation marlstone will destruct due to structural and textural inhomogenesis up to gruss, i.e. it will not meet the requirements of durability.Judging by the results of carried out experiment it should be concluded that by cryogenic weathering the sedimentary rocks (sandstones) and rocks with schistose lithogenic texture (marlstone) are subjected to disintegration. The primary rock samples firmness considerably influences on the disintegration rate.     

Geochemical Characterizations of Source and Depositional Environment of Hydrocarbons in the Lake Albert Rift Basin

Despite the upsurge in hydrocarbon exploration in the Lake Albert Rift Basin(LARB)over the past three decades,systematic characterization of hydrocarbon compositions remains lacking,leading to uncertainties in source rock and oil generation determination.We characterized crude oil compositions and oil sand samples in the northern and southern subbasins of LARB.The relative abundance of normal and branched linear alkanes,hopanes,steranes,and aromatic hydrocarbon suggest that northern and southern hydrocarbons were deposited in anoxic to suboxic lacustrine environments and share similar biological source compositions(i.e.,a mixture of plants and aquatic algae and bacteria).Relative to southern samples,northern samples show more negative δ¹³C values for oils,saturates and aromatics,indicating longer migration paths,and exhibit higher MPI-1,DNR-1 and 4-/1-MDBT ratios,indicating higher maturity.Between the two possible sets of source rocks(upper Miocene and Jurassic strata),the positive δ¹³C values of saturated hydrocarbons(average=-20.5‰)suggest that the upper Miocene lacustrine shale is the most likely candidate.Oleanane index(<5% in our samples)does not exclude either source rock possibility,and C₂₈/C₂₉ regular sterane(average=0.63)may be biased by high terrestrial inputs in a lacustrine setting.Together,our data show that northern and southern oils originate from the same source rocks but different oil kitchens.Given the similar geochemical characteristics of southern and northern oils,previous exploration successes in the northern subbasin likely suggest similar potential in the southern sector,while other elements influencing exploration success must be also evaluated.     

《同一个地质计划》的进展与对策

《同一个地质计划（OneGeology）》最初由英国地质调查局于2006年2月提出,已得到全球地学组织的支持。到2007年底,国际地球科学联合会等10个全球学术团体与国际地学组织、2个跨国公司、2位知名人士和67个国家的地质调查局参加了该计划。《同一个地质计划》是各个国家的地质调查局贡献给国际行星地球年的、约1：100万比例尺的、可在网络上很容易取得最好世界地质图数据的计划。该计划的目标是：使可用的地质图数据能被更多的人使用,使需要的人受益,促进互操作能力的增强。《同一个地质计划》的实施,可以提升全球、大陆、行星、海洋地球科学图的编制和出版的合作能力。深化对一些地区地质问题的研究,并可作为国际地球行星年一个切实可用的成果,提升国家地质调查局的形象;运用管理地学知识的领导能力和经验,通过教育、科学、文化和交流。能够处理全球污染对社会、经济和环境的影响问题。促进全球环境保护公约的执行,减缓自然灾害,使全球经济可持续发展,人们的居住环境更安全、更繁荣。精神生活更丰富、更快乐。因此,实施该计划不仅有现实意义,更有重要而深远的政治意义。     

Cenozoic Sea‐land Transition and its Petroleum Geological Significance in the Northern South China Sea

The process of Cenozoic sea-land changes in the northern South China Sea(SCS)controlled the sedimentary filling pattern and played an important role in the petroleum geological characteristics of the northern marginal sedimentary basins.Under the control of the opening process of the SCS,the northern SCS Cenozoic transgression generally showed the characteristics of early in the east and late in the west,and early in the south and late in the north.The initial transgression occurred in the Eocene in the Taixinan Basin(TXNB)of the eastern SCS,while the transgression occurred until the Pliocene in the Yinggehai Basin(YGHB)of the western SCS.International Ocean Discovery Program(IODP)expeditions(Expeditions 367/368)revealed that the initial transgression of the SCS basin occurred at approximately 34 Ma,which was the initial opening time of the SCS.The period of drastic changes in the sedimentary environment caused by large-scale transgression corresponded to the opening time of the southwestern subbasin(approximately 23 Ma),which also represented the peak of the spreading of the SCS.The sea-land transition process controls the distribution of alternating continent-marine facies,marine facies source rocks and reservoirs in the basins.The marine facies source rocks of the basins in the northern SCS have a trend of gradually becoming younger from east to west,which is consistent with the regional process of gradual transgression from east to west.Regional sea-level changes were comprehensively influenced by SCS opening and global sea-level changes.These processes led to the early development in the east and south and late development in the west and north for the carbonate platform in the SCS.Carbonate platforms form another type of"selfgenerating and self-accumulating"oil-gas reservoir in the northern SCS.The sea-land transition controlled the depositional filling patterns of different basins and laid the foundation of marine deposits for oil and gas resources.The source-reservoircap assemblage in the northern SCS was controlled horizontally by provenance supply and sedimentary environmental changes caused by sea-land transition and vertically by the tectonic evolution of the SCS and regional sea-level changes.     

拉萨地块和羌塘地块多个二叠纪基性岩及一个古特提斯海山的初步古地磁结果:对模拟东冈瓦纳晚古生代裂解的暗示

Detachment of the sliver-like Cimmerian terrane from eastern Gondwana in the Early Permian triggered mafic volcanism in many parts of the rift zone. To understand this tectonic episode we have carried out paleomagnetic investigations on mafic volcanic for-mations that were erupted on key terranes that now form part of Tibet. Specifically, we will present data from sections near Lhasa City (central Lhasa block) and Tuotuohe (central Qiangtang Block) as well as near Gyanyima (Paleotethyan sea-mount) that was emplaced onto the floor of Palaeotethys during the Late Permian. Paleomagnetic plots from each location will be used for tectonic calculations. Our new data will be used to evaluate regional scale models con-cerned with how the Cimmerian terranes in southern and SE Asia (from Iran-Tibet-SW China-Myanmar- Thailand-Sumatra) formerly abutted eastern Gond-wana.     

Permian Fusuline Fauna from the Lower Part of the Lugu Formation in the Central Qiangtang Block and its Geological Implications

A Kubergandian （Kungurian） fusuline fauna from the lower part of the Lugu Formation in the Cuozheqiangma area,central Qiangtang Block is described.This fusuline fauna belongs to the Southern Transitional Zone in palaeobiogeography,and is characterised by the presence of the distinctive bi-temperate genus Monodiexodina and many genera common in lower latitude Tethyan areas such as Parafusulina and Pseudodoliolina.The occurrence of Monodiexodina in the fauna confirms that the seamount-type carbonates of the Lugu Formation did not originate from the Palaeotethys Ocean,but rather from a branch of the Neotethys Ocean after the rifting of the Qiangtang Block from the Tethys Himalaya area in the Artinskian.     

青藏高原双湖地区二叠系玄武岩地球化学及其大地构造意义

对青藏高原羌塘地块中部双湖地区发育的二叠系碱性系列和拉斑系列玄武岩进行了详细的地球化学研究。碱性系列玄武岩富集LILE和LREE,其La/Nb比值和OIB相近,Ti/V比值明显高于典型MORB,在微量元素构造环境判别图解上位于OIB区域。拉斑系列玄武岩具有相对平坦的稀土元素配分模式,和典型MORB相比,其Ti/V比值也明显偏高,在微量元素构造环境判别图解上位于MORB和OIB重合的区域,表明岩石起源于一个低度富集的地幔源区。结合区域地质背景,认为双湖二叠系拉斑系列-碱性系列玄武岩组合可能形成于陆间裂谷到小洋盆环境,这套玄武岩的产出可能代表古特提斯洋沿龙木错—双湖构造带在不同地区的发育程度不同,双湖地区在二叠纪应为一个陆间裂谷到小洋盆环境。     

青藏高原腹地羌塘地体中新生代地层褶皱收缩量研究及其意义

对夹持于金沙江缝合带与班公湖-怒江缝合带之间的羌塘地区,用平衡剖面法统计中新生代地层褶皱收缩量,结果表明中生代以来褶皱吸收的南北向的收缩量最小值为29.3%,与由褶皱的翼间角计算出的27.2%的南北向收缩量大体吻合。受来自印度板块与欧亚板块的南北向挤压力的作用,该地区陆陆碰撞以来吸收了429～500km的南北向缩短,总收缩量的百分比为58.8%～62.5%,而陆陆碰撞以来新近纪地层的褶皱收缩量的最大值为31.6%,由此推断断层引起的南北收缩量大约为27.2%～30.9%。对比各构造层的褶皱收缩量,三叠系构造层的褶皱收缩量平均为29.3%,侏罗-白垩系构造层的褶皱收缩量平均为23.2%,古新统-始新统构造层的褶皱收缩量平均为13.8%,渐新统构造层的褶皱收缩量平均为12.3%,新近系构造层褶皱收缩量平均为17.8%。新近系褶皱收缩量的增大反映高原褶皱收缩增强,与该阶段高原垂向强烈隆升协调。羌塘地体中褶皱收缩量的时空分布显示了与高原各阶段的隆升演化相协调的特点。     

羌塘及南缘地区的地壳结构

通过对INDEPTH III宽频地震资料的处理,采用最新发展的接收函数深度偏移叠加方法,获取羌塘盆地南部及与拉萨地块北侧的剖面。偏移图像勾画了羌塘地区的两盆夹一隆的基底,以及羌塘下地壳内存在的北倾构造序列。冈底斯的基底与羌塘地区有一定的延续性,而拉萨地块的上地壳则完全不同。同时通过与人工深反射地震剖面,发现主要大型的断裂构造在接收函数剖面上均可进行追踪对比,对于羌中隆起和和羌塘南北凹陷的深部成因有启示作用。同时发现班公-怒江缝合带Moho面错断并不明显,而在拉萨地块下方呈现的双Moho在色林错下方进行了合并。在南羌塘Moho面转换波强度不大,而北羌塘又重新恢复正常,推测这是拉萨地块向北的推挤造成羌塘下地壳部分地区重新分异的结果。双Moho的成因有待进一步分析,应该与拉萨地块下方大规模低速物质活动和MHT拆离断层的延伸有关。     

羌塘地块南部晚白垩世火山岩离子探针测年及其对红层时代的约束

羌塘地块南部广泛出露陆相红层,1:25万区域地质调查将大部分红层划归为中新统康托组,但缺乏可靠的年代学依据。野外观测发现火山岩与红层之间存在喷发不整合接触关系,室内从火山岩选出很多岩浆锆石;应用离子探针U-Pb同位素测年方法精确测定岩浆锆石年龄,能够为研究火山喷发期次和红层形成时代提供重要依据。对羌塘地块南部红层内部粗面安山岩夹层—比洛错火山岩和扎加藏布北侧红层上覆安山岩,挑选岩浆锆石进行高精度的离子探针U-Pb同位素测年,发现比洛错粗面安山岩锆石206Pb/238U同位素年龄为(83.3±1.3)Ma,扎加藏布北侧安山岩锆石206Pb/238U同位素年龄为(75.65±0.82)Ma。这些年龄良好地揭示了晚白垩世不同期次的火山喷发时代,同时为红层形成时代和红层盆地演化提供了重要的年代学约束。根据比洛错和扎加藏布北侧火山岩的锆石U-Pb同位素测年资料,将羌塘盆地南部红层时代归属上白垩统阿布山组,这对分析羌塘地块南部油气地质构造保存条件和构造地貌演化具有重要意义。     

西藏双湖古近纪唢呐湖组碎屑锆石U-Pb年龄与古海拔高度

青藏高原北部古近纪晚期大面积发育唢呐湖组湖相沉积,主要为砖红色、棕色、灰白色泥灰岩、泥岩、粉砂岩互层,夹石膏层和灰岩,广泛出露于羌塘中部、可可西里、东昆仑南部,形成时代为41.1±0.8~32.5!0.3Ma,向可可西里东部过渡为雅西错群。对双湖采坑唢呐湖组上部湖相沉积地层进行详细观测和系统取样,对泥灰岩和粘土岩样品选碎屑锆石作LA-MC-ICP-MS U-Pb同位素测年,对不同层位泥灰岩、粘土岩、灰岩样品作碳、氧同位素分析,结合区域地质相关资料,良好揭示了碎屑锆石来源、沉积地貌环境及古海拔高度。双湖采坑唢呐湖组碎屑锆石绝大部分为岩浆锆石,统计分析碎屑锆石U-Pb年龄,发现存在4期峰值,分别为280~200Ma、780~830Ma、1920~1790Ma、2600~2360Ma;对比区域地质和岩浆岩测年资料,推断晚二叠世—三叠纪(280~200Ma)碎屑锆石主要来自于羌中隆起岩浆岩,新元古代中期(~800Ma)、古元古代晚期(~1800Ma)、太古宙末期—古元古代初期(~2500Ma)碎屑锆石主要来自于东昆仑造山带。双湖采坑碎屑锆石部分测点U-Pb同位素呈线性分布,交点年龄及谐和年龄为1883!51~1837!12Ma、2483!24~2520!37Ma,对应东昆仑造山带早前寒武纪2期岩浆热事件年龄。根据唢呐湖组湖相沉积空间分布和碎屑锆石U-Pb年龄统计分布,推断青藏高原北部古近纪晚期发育自北向南流动的古水系,古洪流将东昆仑造山带出露地表的前寒武纪基底岩浆锆石自北向南长距离搬运,汇聚于双湖古湖盆并沉积于唢呐湖组。根据双湖采坑唢呐湖组湖相沉积碳同位素和氧同位素,估算双湖古湖盆35~34Ma古海拔高度为3427~3510m,这与应用Airy均衡模式根据地壳厚度和密度变化估算的古海拔高度在误差范围内基本吻合。     

羌塘盆地结构构造与油气勘探方向

羌塘盆地是我国陆域大型中生代海相沉积盆地,富含烃源岩,但结构构造非常复杂。结合野外观测及相关资料对地震反射剖面进行地质构造详细解释,良好地揭示了羌塘盆地结构和深部构造。羌塘盆地逆冲推覆构造延伸存在显著差别,北羌塘凹陷多格错仁逆冲推覆构造、阿木错逆冲推覆构造与南羌塘凹陷肖茶卡—双湖逆冲推覆构造、多玛—其香错逆冲推覆构造仅发育于盆地表层0~3km深度范围,北羌塘凹陷龙尾错逆冲推覆构造、羌中隆起北缘逆冲推覆构造、南羌塘凹陷赛布错—扎加藏布逆冲推覆构造、拉萨地块北缘色林错逆冲推覆构造系统自地表向深部延伸深度超过6km,羌塘盆地深部还发育中生界底部逆冲系和基底逆冲系,伴有不同规模的褶皱构造。逆冲推覆构造形成活动时代包括晚白垩世、古近纪早期和古近纪晚期,晚白垩世与古近纪早期逆冲推覆构造运动导致构造隆升的裂变径迹年龄分别为87±5~75±4Ma、64±5~46±4Ma。经过多期逆冲推覆构造改造和褶皱变形,羌塘盆地中生界海相沉积地层与烃源岩显著增厚,为新生代晚期二次生烃及油气成藏提供了非常有利的地质构造条件;北羌塘凹陷发育万安湖向斜、半岛湖背斜、东湖向斜、阿木错向斜,南羌塘凹陷发育宁日圈闭、鲁雄错背斜、诺尔玛错圈闭、协德圈闭、崩则错圈闭,羌中隆起下伏侏罗系和三叠系烃源岩,色林错下白垩统下伏古近纪湖相沉积,这些构造部位都是油气勘探的重要靶区。     

澜沧江河流沉积物碎屑锆石U-Pb年龄、Hf同位素组成及其地质意义

为研究澜沧江沉积物的物质来源及相邻地块的地壳生长和演化规律,利用LA-MC-ICP-MS分析技术,对澜沧江河流沉积物碎屑锆石进行了U-Pb年龄和Hf同位素研究。结果表明：锆石U-Pb年龄主要有5个年龄段,分别是＜177 Ma、201~418 Ma、428~544 Ma、581~1189 Ma和1406~2533 Ma,主要峰值为260 Ma、788 Ma、1 827 Ma和2 474 Ma。其年龄分布特征与北羌塘地块的年龄分布非常一致,说明澜沧江沉积物主要来源于北羌塘地块;结合Hf同位素分析结果,能够反映源区北羌塘地块的形成与演化历史。新太古代-中元古代是北羌塘地块从亏损地幔物质增生的地壳持续生长阶段,它们构成现今北羌塘地块全部地壳物质的78%以上,此后直到0.64 Ga,北羌塘地块的地壳增生作用基本结束。     

西藏羌塘南部地区的冰海杂砾岩及其成因

青藏高原及邻区广泛分布的漂砾层、杂砾岩、含砾板岩是一种特殊的冰海相沉积岩，称为冰海杂砾岩（Ｉｃｅ－ｓｅａＭｉｘ－ｃｏｎｇｌｏｍｅｒａｔｅｓ）。它们和一起产出的冷水型动物群、耐冷植物群视为这一地区冈瓦纳相最典型的标志，代表着冈瓦纳大陆上塔尔切尔（Ｔａｌｃｈｉｒ）冰期所影响的时间和空间。除“标准型”冰海杂砾岩外，羌塘腹地发现了蛇绿质和钙质冰海杂砾岩。这两种冰海杂砾岩的发现，不但丰富了冰海杂砾岩的家族成员，同时也为冰海沉积、物质来源问题、冈瓦纳大陆北界及特提斯演化研究提供了新的信息。经研究，冰海杂砾岩中的砾石来自印度半岛──冈瓦纳大陆本体，以冰筏为载体融冰落石成因。